Fixing device for a cavity wall

ABSTRACT

A fixing device includes a sleeve portion and an engagement portion which are spaced apart but which are interconnected by two flexible strut members, each of which includes short and long arms. A screw can be inserted through a central bore in the sleeve portion so that its end engages a bore in the engagement portion to initially hold the engagement portion in a fixed position relative to the sleeve portion and thereby resist flexing movement of the strut members. Upon subsequent tightening of the screw, the sleeve and engagement portions are caused to move together, thereby flexing the strut members outwardly.

BACKGROUND OF THE INVENTION

This invention relates to a fixing device for a cavity wall, such as awall faced with plasterboard.

SUMMARY OF THE INVENTION

According to the present invention, such a fixing device comprises asleeve portion adapted to receive therethrough a screw or similar fixingelement, an engagement portion spaced from the sleeve portion andadapted to engage an end portion of the screw, and at least one flexiblestrut member connecting the engagement portion to the sleeve portion,the arrangement being such that engagement of the screw with theengagement portion holds the latter in a fixed position relative to thesleeve portion and thereby resists flexing movement of the at least onestrut member. Conveniently, tightening of the screw causes theengagement portion to move towards the sleeve portion and thereby causethe at least one strut member to flex outwardly of the device.

Preferably, the at least one or each strut member comprises a relativelylong arm connected to the engagement portion and a relatively short armconnected to the sleeve portion, such that the point where the arms arejoined moves forwardly as well as outwardly of the device as the screwis tightened.

Advantageously, the at least one or each strut member has a fingerextending forwardly of the device substantially from the point where therelatively long and short arms are joined together.

Conveniently, the at least one or each strut member is connected to theengagement portion at a position which is spaced from the end of theengagement portion nearest to the sleeve portion.

Desirably, the at least one or each strut member normally extendslaterally beyond the sleeve portion but can be flexed so as to be atleast substantially flush with the sleeve portion, so as to facilitateentry of the device into a bore in the cavity wall. In this case, therelatively long and short arms can be so dimensioned that, when the atleast one or each strut member is thusly flexed, the point where thearms are joined lies adjacent to the end of the engagement portionnearest to the sleeve portion.

Preferably, the end of the engagement portion nearest to the sleeveportion has a bore for receiving the end portion of the screw.

Desirably, the device comprises two such strut members extendingrespectively in opposite lateral directions from the sleeve and theengagement portions.

Conveniently, the sleeve portion has formations on its outer surface forengaging a side wall of a bore in the cavity wall in which the device isinserted in use.

Advantageously the sleeve portion is radially expandable.

BRIEF DESCRIPTION OF THE DRAWING

The invention will now be further described, by way of example only,with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of the fixing device according to thepresent invention;

FIG. 2 is a side view showing the device in its normal condition;

FIG. 3 is a side view showing the device in a condition ready forinsertion into a bore in a cavity wall; and

FIG. 4 is a cross sectional side view showing the device in actual usein a cavity wall.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The illustrated fixing device, as shown in FIGS. 1-4, is made of aplastic material and comprises a sleeve portion 10 having a central holeor bore 11 for receiving a screw or similar fixing element 12 (see FIG.4). The device also comprises an engagement portion 13 which also has acentral bore 14 to receive an end portion of the screw, the engagementportion 13 being integrally connected to the sleeve portion 10 by meansof a pair of flexible strut members 15 which extend respectively inopposite lateral directions from the portions 10 and 13. Each strutmember 15 is composed of a relatively short arm 16 connected to thesleeve portion 10 and a relatively long arm 17 connected to an end ofthe engagement portion 13 remote from the sleeve portion 10. A finger 18extends forwardly from the point where the two arms 16, 17 meet in eachstrut member 15, the outwardly-facing surface of the finger 18 beingprovided with projections 19.

In order to insert the device into a bore 20 in one leaf 21 (e.g., ofplasterboard) of a cavity wall (see FIG. 4), the strut members 15 can becompressed inwardly so that they and the fingers 18 lie substantiallyflush with the outer surface of the sleeve portion 10, as depicted inFIG. 3. The various parts of the device are so dimensioned that, underthis condition, the points where the arms 16 and 17 are joined togetherlie closely adjacent to the end of the engagement portion 13 nearest tothe sleeve portion 10. The part of the device including the engagementportion 13, the strut members 15 and the fingers 18 can then be passedinto the bore 20, whereupon the sleeve portion 10 can also be hammeredor pressed home into the bore. Once this has been completed, the strutmembers 15 expand outwardly under their own natural resilience so thatthe fingers 18 confront a surface 22 of the wall 21 which faces into thecavity.

To facilitate insertion of the sleeve portion 10 into the bore 20, theouter surface of the portion 10 is slightly tapered so that its diameterincreases in a direction away from the engagement portion 13. The outersurface is also provided with various formations which serve to resistsubsequent removal of the sleeve portion 10 from the bore 20, namely,longitudinally-extending sawtooth ridges 23 andcircumferentially-extending broken ridges 24. The sleeve portion 10 alsoterminates in a flange 25 which engages an outwardly facing surface 26of the wall 21 to prevent the device from passing completely through thebore 20.

In order to secure an article 27 (such as a shelf bracket) to the wall21, the screw 12 is passed through a bore in the article 27 and its endportion is pressed into the bore 11 in the sleeve portion 10 as isconventional practice with fixing devices of this general nature. Thescrew 12 is then turned, causing the threads thereon to bite into thematerial of the sleeve portion 10 and the screw 12 to penetrate the bore11. During such penetration, longitudinal splits 28 in the sleeveportion 10 enable the sleeve portion 10 to expand outwardly to urge theformations 23, 24 into close contact with the side walls of the bore 20.

Upon continued turning of the screw 12, its end portion passes out ofthe opposite end of the bore 11 and into engagement with the bore 14 inthe portion 13. The bore 14 is dimensioned so that the threads on thescrew 12 will bite into the material of the portion 13, thereby holdingthe portion 13 in a fixed position relative to the sleeve portion 10.Under this condition, the strut members 15 and the fingers 18 aresimilarly held in a fixed position relative to the sleeve portion 10.Further tightening of the screw 12 will tend to move the engagementportion 13 forwardly towards the sleeve portion 10, and the resultantlongitudinal compression of the device causes the strut members 15 toflex further outwardly. Because of the geometry of the arms 16 and 17,the fingers 18 are thereby moved not only outwardly of the device butforwardly as well, bringing their forward ends into preferably tightengagement with the wall surface 22.

The fixing device thus provides secure mounting of the article 27 on thewall 21, primarily by virtue of the tight engagement of the sleeveportion 10 within the bore 20, but also due to engagement of the fingers18 with the wall surface 22. The device is therefore above to supportrather heavier loads than many conventional cavity wall fixing devices.In the event that the sleeve portion 10 should fail, the article 27 willstill be held in place by the action of the strut members 15 and thefingers 18.

What is claimed is:
 1. A fixing device for a cavity wall, comprising:asleeve portion adapted to receive a fixing element therethrough; anengagement portion spaced from the sleeve portion and adapted to engagean end portion of the fixing element; at least one flexible strut memberconnecting the engagement portion to the sleeve portion, the at leastone flexible strut member comprising a relatively long arm connected tothe engagement portion and a relatively short arm connected to thesleeve portion, the relatively long arm and the relatively shot armbeing connected together at a point; and a finger extending forwardly ofthe device substantially from the point where the relatively long andshort arms are joined together; the arrangement being such thatengagement of the fixing element with the engagement portion holds thelatter in a fixed position relative to the sleeve portion and therebyresists flexing movements of the at least one strut member, andtightening of the fixing element causes the engagement portion to movetowards the sleeve portion and thereby causes the at least one strutmember to flex outwardly of the device and the point at which therelative long arm and the relatively short arm are joined together tomove forwardly as well as outwardly of the device, wherein the sleeveportion is radially expandable.
 2. The fixing device as claimed in claim1, wherein the at least one strut member is connected to the engagementportion at a position which is spaced from the end of the engagementportion nearest to the sleeve portion.
 3. The fixing device as claimedin claim 1, wherein the at least one strut member normally extendslaterally beyond the sleeve portion but can be flexed so as to be atleast substantially flush with the sleeve portion, to facilitate entryof the device into a bore in a cavity wall.
 4. The fixing device asclaimed in claim 1, wherein the relatively long and short arms are sodimensioned that, when the at least one strut member is flexed, thepoint where the arms are joined lies adjacent to the end of theengagement portion nearest to the sleeve portion.
 5. The fixing deviceas claimed in claim 1, wherein the end of the engagement portion nearestto the sleeve portion has a bore for receiving the end portion of thefixing element.
 6. The fixing device as claimed in claim 1, comprisingtwo such strut members extending respectively in opposite lateraldirections from the sleeve and engagement portions.
 7. The fixing deviceas claimed in claim 1, wherein the sleeve portion has formations on itsouter surface for engaging a side wall of a bore in a cavity wall inwhich the device is inserted in use.
 8. A fixing device for a cavitywall, comprising;a sleeve portion adapted to receive a fixing elementtherethrough; an engagement portion spaced from the sleeve portion andadapted to engage an end portion of the fixing element; at least oneflexible strut member connecting the engagement portion to the sleeveportion, the at least one flexible strut member comprising a relativelylong arm connected to the engagement portion and a relatively short armconnected to the sleeve portion, the relatively long arm and therelatively short arm being connected together at a point; and a fingerextending forwardly of the device substantially from the point where therelatively long and short arms are joined together; the arrangementbeing such that engagement of the fixing element with the engagementportion holds the latter in a fixed position relative to the sleeveportion and thereby resists flexing movements of the at least one strutmember, and tightening of the fixing element causes the engagementportion to move towards the sleeve portion and thereby causes the atleast one strut member to flex outwardly of the device and the point atwhich the relative long arm and the relatively short arm are joinedtogether to move forwardly as well as outwardly of the device, andwherein the sleeve portion has formations on its outer surface forengaging a side wall of a bore in a cavity wall in which the device isinserted in use.
 9. The fixing device as claimed in claim 8, wherein theat least one strut member is connected to the engagement portion at aposition which is spaced from the end of the engagement portion nearestto the sleeve portion.
 10. The fixing device as claimed in claim 8,wherein the at least one strut member normally extends laterally beyondthe sleeve portion but can be flexed so as to be at least substantiallyflush with the sleeve portion, to facilitate entry of the device into abore in a cavity wall.
 11. The fixing device as claimed in claim 8,wherein the relatively long and short arms are so dimensioned that, whenthe at least one strut member is flexed, the point where the arms arejoined lies adjecent to the end of the engagement portion nearest to thesleeve portion.
 12. The fixing device as claimed in claim 8, wherein theend of the engagement portion nearest to the sleeve portion has a borefor receiving the end portion of the fixing element.
 13. The fixingdevice as claimed in claim 8, comprising two such strut membersextending respectively in opposite lateral directions from the sleeveand engagement portions.